Method and apparatus for deflecting bore holes in sub-surface formations



Aug; 30, 1955 A. F. PICKARD METHOD AND APPARATUS FOR DEFLECTINGy BORE HOLES IN SUB-SURFACE FORMATIONS 5 Sheets-Sheet 1 Filed Jan. 7, 1950 /e/C-Al INVENTOR.

F. P/c/m RD' ATToR/ve'yr Aug. 30, 1955 A. F. PlcKARD 2,716,539

METHOD AND APPARATUS F DEFLECTTNG BoRE HOLES IN sus-SURF E FORMATIONS s sheets-sheet 2 Filed Jan. 7, 1950 VII INVENTOR. A1. BERT/: P/CKARD BY A Tvc/@vs rs Aug. 30, 1955v A F PlCKARD 2,716,539

METHOD AND APPRA-TUS FOR DEFLECTING BORE HOLES IN SUB-SURFACE FORMATIONS Filedy Jan. 7, 1950 3 Sheets-Sheet 3 INVENTOR. /L BERT F.P/CKARD 87M, MMM

United States Patent O METHOD AND APPARATUS FOR DEFLECTING BORE HOLES IN SUB-SURFACE FORMATIONS Albert F. Pickard, Minneapolis, Minn., assigner to E. J. Longyear Company, Minneapolis, Minn., a corporation of Delaware Application January 7, 1950, Serial No. 137,426

4 Claims. (Cl. Z55-1.6)

`In the drilling of deep bore holes in sub-surface formations, the direction of the hole frequently changes due to the relatively great transversel flexibility of the string of tubing that is used for carrying and rotating the bit. In no other mechanical drilling problem is there used a length of drill rod or drill pipe such as is regularly employed in rotary drilling of deep bore holes. For example, in exploratory and oil well drilling operations the depth of hole may be many thousands of feet, whereas the diameter of the tubular shaft used for rotating the bit is measured in inches. The drill rod, which is almost always tubular, easily bends when used in such great lengths, and accordingly the rotary bit at the bottom of the hole can and does assume a direction of travel bearing no relationship to the direction of the hole at the surface. Consequently, in the drilling of such deep holes it is usual practice, periodically, to determine the direction 2,716,539 Patented Aug. 30, 1955 ice and apparatus for delecting bore holes in sub-surface formations which can be carried out by relativelyy unskilled operators.

surface formations and to provide methods and apparatus which can be utilized for deflecting bore holes, re-

-gardless of the direction of progress of the hole, Whether up or down, horizontally or any intermediate direction.

lt is another object of the invention to provide methods of deilecting bore holes in sub-surface formations utiliz- 0f the bore hole as the bit progresses downwardly and to take appropriate steps for deilecting the bit, in order to maintain straight, or relatively straight, the direction 0f the hole. In some instances it is 4desirable to start the -hole in a given direction and then as the bit progresses, to

cause the bit to be deflected so that the hole is curved 1 and assumes another direction. Such practice of deflecting holes is useful where it is expensive or diflicult to set up the drill rig directly over or in line with the region to be reached by a straighthole, and is also useful for avoiding certain formations through which progress of the drill may be expected to be accompanied with ditliculties.

Heretofore, the deflection of the bit for the purpose of deilecting .the hole has been accomplished by the use of wedges which were set in the hole and then permitted to remain in. the hole for the purpose of deilecting the bit. After the bit had progressed past the wedge thus set, the wedge forms a part of the hole wall and is to remain in the hole and is not re-usable. These wedges are relatively expensive, and since each wedge is incapable of producing more than a few degrees of deflection of the hole, many are needed in order to produce a substantial change in direction of the hole. As: a result, changing the direction of a bore hole is an expensive proposition amounting, in many instances, to several thousands of dollars for wedges alone, to say nothing of the cost of thetime involved for placing them'in the holes.

It is an object of the present invention to provide improved methods and apparatus for dellecting the direction of bore holes in sub-surface formations.

It is a further object of the invention to provide methodsl and apparatus for deilecting bore holes in sub-surface formations wherein the utilities used for such purposes may be recovered andr re-used many times without deterioration other than normal wear.

It is a further object of theinvcntion to provide methods and apparatus for more economically deflecting bore holes in sub-surface formations and for detlecting them ing a minimum of operational steps.

lt is a further object of the invention to provide methods and apparatus for dellecting bore holes deep in subsurface formations wherein all of the deilecting mechanisms are withdrawn from the bore hole and the bore hole left in condition such that removal or withdrawal of bits therefrom is not'accompanied by hazard to the bit or' the bore hole.

lt is a further object of the invention to provide methods and apparatus for deflecting bore holes wherein cementing of the hole is not required.

It is a further object of the invention to provide methcds and apparatus for deflecting and continuing the drilling of bore holes without a reduction in the diameter of the bore hole. l

Other and further objects of the invention are those inherent in the apparatus herein illustrated described and claimed.

The invention is illustrated with reference to the drawings wherein corresponding numerals indicate the same parts and in which:

Figure l is a fragmentary sectional view, which maybe a longitudinal section illustrating a sub-surface formation with a normal rotary bit and a reaming shell therein at the bottom of a hole being produced by the bit;

Figure 2 is likewise a sectional view through a subsurface formation, showing a taper bit in place for producing a taper, as in accordance with the preferredstep in the method of carrying out the instant invention;

Figure 3 is a sectional View of sub-surface formation showing the improved deilecting apparatus of the present invention attached to standard casing and set in place preliminarily andin a random position without the direction of deflection having been determined;

Figure 4 corresponds to Figure 3 and is a sectional View through sub-surface formation showing the deilecting instrumentality in place on the end of a string of casing and illustrating the apparatus and method of determining the direction of the bore hole by means of a clinometer;

Figure 5 corresponds to Figures 3 and 4 and shows a sectional View through'sub-surface formation with the casing string carrying the bore hole deilecting instrumentality rotated and hence re-oriented in a direction so as to produce deflection of the hole in a desired direction;

y Figure 6 corresponds to Figures 3-5 and shows a sectional view through sub-surface formation, and illustrates a further step in the method and utilizing apparatus ofthe invention wherein a smaller size bit is lowered through the casing and through the deflecting apparatus and is about to be used for producing a smaller diameter extension of the original hole, butin the desired deflected direction;

Figure 7 is a sectional view through sub-surface formation showing the hole as produced by the various steps illustrated in Figures 1-6, but with the deflection appara- 3 tus and the casing on which it is carried, as in Figures 3-6 withdrawn from the hole and a reaming bit on drill rod lowered and in a position about to enter the smaller size hole;

Figure 8 corresponds to Figure 7 and shows the reamingbit on Figure 7 progressed downward in its reaming operation; Figure 9 corresponds to Figures 7 and 8 but shows the reaming bit further along in its reaming operation and illustrates how the bore hole of original large diameter is resumed along the deflected direction;

Figure l() is a fragmentary transverse sectional view taken along the line and in the direction of arrows 10-10 of Figure 3;

Figure 11 is a fragmentary transverse sectional view taken along the line and in the direction of arrows 11-11 of Figure 4;

Figure 12 is a fragmentary transverse sectional view taken along the line and in the direction of arrows 12-12 of Figure 3;

Figure 13 is an enlarged separated view partly in longitudinal section illustrating the clinometer apparatus which, in Figure 4, is shown assembled with other portions of the apparatus;

' Figure 14 is a view, taken along the line and in the direction of arrows 14-14 of Figure 13;

Figure l is a vertical elevational view, partly broken away and therefore in longitudinal section, illustrating the clinometer tube which is shown in position in Figure 13, removed from the apparatus and in a position to take the reading on the clinometer tube;

Figure 16 corresponds to Figure l5, being a side elevational View taken along the line and in the direction of arrows 16-16 of Figure 15;

Figure 17 is a plan view of a portion of the drilling platform at the surface, illustrating index marks on the platform or other reference surface by means of which the operator may judge and correct the angular direction of the deilecting instrumentality as placed in the hole.

Referring to the drawings, a sub-surface formation is illustrated at in Figure 1 and in the remaining figures. The sub-surface formation may be considered as deep in the rock forming the earths crust and may be considered as hundreds or thousands of feet from the surface where the drill rig is situated. It is well known, of course, that where drilling is initiated from the surface, through drift overlaying the underlying rock formations, it is customary to drill through the drift and to case the hole thus formed down to rock level with steel casing of suitable size so as to prevent caving through the overlaying drift. However, deep in the rock formation there is usually no casing, the hole wall being maintained by the strength of the formation itself assisted by the drilling fluid. Thus, in Figure 1 the drill rod at 11 carries a reaming shell at 12 below which there is situated the usual rotary bit 15.

At any depth the operator can by suitable instruments known in the art determine with comparative certainty the direction in which the hole is progressing, and when it is determined that the direction of the drill hole is not such as is desired, the direction of drilling must be con rected. In accordance with this invention, such correction of drilling direction is accomplished in a plurality of novel manipulative steps and by the use of novel combinations of apparatus as follows:

As an optional but preferred first step, when the direction is to be changed, there is first inserted a taper bit, as illustrated by Figure 2, and a taper is drilled. Thus, in Figure 2 there is illustrated a taper bit at 16 attached to the lower end of the string of rods 11. Even though the members 11 are actually tubes screwed together, throughout this specification the term drill rods will be used, since such nomenclature is almost universal among drillers. Such rods are screwed together, end to end by couplings, and collectively are called a string of drill rods. For the purpose of this discussion the term drill 4 rods may include a core barrel on the end of the drill rod, as is commonly used fin exploratory drilling. The change from the bit 15 and 4reaming shell 12 to the bit 16 is accomplished by pulling the entire string of drill rods 11 and unscrewing them, one length at a time until the bit end is out, after which the reaming shell 12 and bit 15 are removed and the taper bit 16 is then attached and the drill string re-assembled, a length at a time, and lowered until bit 16 is on the bottom of the hole, whereupon rotation is resumed sufficiently to produce a taper at the bottom of the drill hole, until the conical tapered surface 17 is made.

The reason for optionally performing this preferred step of producing a taper at 17 is that in the hole, with the direction ultimately deflected to the correct direction, in accordance with the present invention, if the taper bit 16 were not used, a shoulder would be presented at the level or change of direction (as shownl at 101 of Figure 9), which would thereafter be the source of hazard when bits are lowered later on during further drilling. The use of the tapered bit 16 for the production of the tapered surface 17 is not absolutely essential and may be dispensed with where care is exercised in lowering the bit during later drilling operation, but the use of the tapered bit is recommended and is preferred.

The next step in the method of the invention and utilizing the apparatus thereof is carried out by removing the string of drill rods and the taper bit 16 from the hole, and by then assembling onto the appropriate size casing for the hole and then lowering a bit-deflecting instrumentality generally designated 20 to which attention is now directed.

The bit-deflecting instrumentality 20, hereinafter called the bit deector consists of an elongated metallic member, preferably of hard steel having a cylindrical outer surface at 21 of a size such that it can be lowered conveniently into the hole 9 produced by the bit 15 and reaming shell of Figure 1. Usually the diameter of member 20 is about intermediate between the diameter of the hole produced by a standard bit and reamer, and the diameter of the standard casing for such hole. No attempt is made to show these slight differences between the various diameters other'than to show the clearance between the hole 9 and member 20 and the hole 9 and casing 13. In the drawings such clearance is exaggerated. The bit-dellectorv 20 has a threaded coupling end 22 formed at its upper end, provided with standard threads so that the entire member 20 can be screwed onto the end of the lowermost length of standard casing in the string 13 of drill rod 11. The inner diameter of the standard casing 13, as .shown at 24, is the same as the diameter of the hole 25 through the bit-deilector 20 just below the coupling end. 22. The upper portion ofthe bit-deflector 20 is designated as the coupling end 22.

The outer surfaceV 21 at the coupling end continues downwardly to the opposite or lower end 26 and is cylindrical and of the same diameter as casing 13 or just slightly larger, as explained above. Below the coupling end 22 of the bit-deector 20 the opening or hole 25 merges into'the surface 28 which is also cylindrical. Surface 28 corresponds preferably to the diameter of the next smaller sizeof standard'drill bit than that used at 15 in Figure 1, although it may, if desired, be the same as the diameter of a bit which is several sizes smaller. T hus, the surface 28 is a cylindrical surface and extends from the coupling hole 25 on down to the lower end 26 of the member 20. However, the axis of the cylindrical surface 28 is at a slight angle to the axis of the outer cylindrical surface 21. Thus, the axis of the cylindrical surface 21 is illustrated by the line 31 which is also the axis of the coupling 22 and casing 13, whereas the axis of the smaller, cylindrical'surface 28 is shown by the line 32, there being a slight angle, usually 1 degree to 4 degrees between the two axes. The two axes 31 and 32 intersect preferably in the region ranging from the coupling end 22 to slightly below the coupling. vIn this illustration the intersection is slightly below theicoupling.

Referring to Figure 12, which isv a View of: the lower end of the bit-deiiector, it will be noted how the outer cylindrical surface 21 corresponds to that ofthe drill hole being produced, less clearance, whereas-"the inner partial cylindrical surface 28 isy offset slightly and at the lower end 35 of the bit-detiector by anamount lillustrated by the dimension 38, which is the distance lbetween t the axes 31 and 32 at the bottom end 35'of'the bitdeilector. v

The diameter of the inner cylindrical t. surface 28 is approximately equal to thediameter' of the selected smaller size standard bit, as compared: with bit 15, Figure 1', and hence such a selected smaller size standardi bitv will t in the circle shown by the dotted-lines 36 and surface 28 between the hole walll at 30 and the surface 28 at the lower edge 35 of the bit-d'eector 20; Such a smaller size standard bit will thus bein contact with the original bore hole 9 of the original diameter at the place 30 and the bit is displacedl from die original axis of 'the original bore hole by the amountof dimension 38. The dimension 38 is approximately equal to the thickness 46, Figure 3, and is also the same as the displacement of the axis (line 32, Figures 3-5) of the smallerbit (circle 36-28, Figure l2) from the axis (line 31,. Figures 3-5) of the original bore hole at the bottom of the member 20. Stated another way, the diameter of the smaller bit (circle 36-28 of Figure l2) is equal to or very slightly less than the diameter of the original hole being produced minus the thickness 46 of the bit-deector 20 at the bottom. The surface 28of the bit-deflector 20 is cylindrical and ts the diameter of the chosen smaller size bit.

The bit-deflector 20 is preferably, 'though not necessarily, cut away along the line 40 near the coupling end 22 and then cut away longitudinally along the line 42. This cut-away portion is provided mainly to'allowfaccess for placing a keying blockv 45, as shown inrFigures 3-5, but access to such a keying block or key can be-provided in other ways and the deflecting instrumentality need not necessarily be cut away along the lines 40 or 42.

It is noted in passing that the increased thickness of the deflecting instrumentality, as shown by the dimension 46 in Figure 3, means that if the wall were not cut away along the lines 40-42, the wall at the opposite side would feather out to a knife edge, at least at one point, and hence the cut-away portion of the wall' is the weakest portion and its removal .does -not seriously reduce the strength of the device. It may be left in place or removed, as desired. I

Adjacent the coupling end 22 or elsewhere on the bitdeflector 20 there is provided a keying block 4S orl other land or surface, by means of which the angular position of the bit-deflector 20 can be determined at the surface. At the surface where the drill. rig is located, there is provided on the drill platform, or on some fixed reference surface, a quadrant marked-off in degrees, as: shown by the quadrant 48 in Figure 17. These can be simple marks on a board surrounding the casing at the surfacey or may be a formal quadrant and are used by the operator -in judging the angular position of the various ydevicesplaced in the hole. 1

The bit-deflector 20 is provided with thetla'nd 4S. This land serves to locate angularlythe clinometer shown generally rat 50 in Figure 4 `and separated in Figure 13. Once used the land 4S is sheared or drilled` out and is replaced the next time the bit-deflector is used. Hence, the only requirement in regard to land is that it should be capable of being easily sheared or drilled away and need not be of the type shown inv Figure 4 but can be a knob, land, projection or groove of any sort into the'interior of the bit-deiiector 20 and should preferably be near the coupling end 22. i n

When the bit-deector 2t 'is cut away along` the lines 40-42, as is preferred, the land 45 is easily accessible for' replacement and is preferably a hard wood block which is held in place by the rivets 51, as shown in Figures l0 and ll'. A heavy brass screw or pin through the ywall of the bit-deflector 20 would serve aswell as a locating device and is included within the purview of the invention.

Referring to Figures 4 and 13, particularly, the clinometer generally designated 50 consists of a body portion 52 having screw threads at 53 sothat the cap 54 'can be screwed on, the cap in turn being providedy with screw threads at 55 so that the entire clinometer canl be attached to the lower end of the string of drill rods 56. The diameter of the clinometer 50 and rods 56 is such that they can be lowered through casing 13; The cou'- pling member 54-55 is provided with a holeat 54-54' in order to permit water entrained in the'fstring of drill rods 56 to drain `out when the rods are pulled from the hole. t

The clinometer has a hollow cylindrical cavity at 57 in which there is placed a glass tube 58 provided withvr a rubber stopper at 59. In use the glass tube is partially filled with a solution of hydrolluoric acidy 60.v The lower end` of the clinometer body 52 is cut away along the longitudinal diametric plane 61 and is provided with a chamfer at 62; Thus, in transverse section, the lower end of the member 52 of the clinometer is the half circular shape shown at 63 in Figure ll and is adapted to make a sliding fit with the corresponding surface 64 of the` block or loca-ting land 45 which is provided in the coupling end 22 of the bit-deflector 20. The only requirement in regard to the shape of surfaces 61 and 64 is that they shouldt each other with a longitudinal sliding fit and all Variations of such mating surfaces will be understood to be Within the `purview of the instant invention.

viti ywillbe noted that the clinometer body and the string` of drill tubes 56 are of the selected smaller diameter, as compared with the string of casing 13 and the string of drill? rods 56 land clinometer 50 thus lower neatly through casing 13 and consequently passes through the coupling at 22l of the bit-deector 20.

When the bit deflector 20 is first lowered'into the hole, its position is random and bears only achance relationship to the desired position for dellecting the hole. Hence, the bi-t-deiiector must be rotated more or less to a new position if .it is to serve to correct the direction of the hole. lIt would only be chance, if, when originally lowered, ythe bit-'deector 20 happened to be in the correct position to correct the direction of the hole. Thus, in respect tho-Figure 3 it can` be assumed that the bit-deilector 20, when: originally lowered would produce a deflection olf to the left, as shown in Figure 3, at the bottom and that the driller actually desires to bring the hole to a vertical position with respect to the sheet of drawings, or vertical in respect to the position shown in Figure3, which hence would be the position of Figure 5. It is therefore assumed, for purposes of illustration herein that the bit-deilector 20 is in exactly opposite direction, the surface 28 in Figure 3 oriented so that, if used in that position, it would increase the amount of deflection to the left, which would not correct the hole, but make it' worse. Stated another way, the bit-deflector Ztl must be rotated degrees from the position of Figure 3 to the position `of Figure 5.

I The next step in the process is the lowering of the clinometer at 50, as shown in Figure 4. The glass tube 58 is partially filled withhydrouoric acid 60, is stopp'ered at 59 and set in the clinometer body with the scratch mark 73 of the glass tube and aligned with the marks 72-72A of the clinometer body. It is noted that mark 72 extends lengthwise of the long side 61A of the clinometer body and corresponding mark 72A is carried up over the threads 53 for easy reading with reference to vmark 73 on tube 58. The clinometer is coupled to the string 56 of drill rods and loweredth'rough the holein casing 13. When reaching the level of the coupling 22 the operator rotates the string of drill rods 56 by hand until the surface 62 of the clinometer body keys into and finds its way downward into the space between the block 45 and the opposite part of hole 25. Then the operator lowers the clinometer body 5t) to the position shown in Figure 4, and the clinometer body 50 is accordingly in a fixed position with reference to the bit-deector 20. Hence, the operator will know at the surface that the clinometer 50 has been set at a fixed position with reference to the bit-deflector 20, which in turn is set at random in the hole, but the operator still does not know the amount of angular rotation of the bit-detlector that will be needed to bring the direction of the hole back towards a correct direction.

The operator then permits the clinometer 50 to remain in the hole for a given period, such as 30 minutes, and then removes it.

When the clinorneter Si) is brought to the surface, the operator removes the glass tube 53 and dumps out the hydrotluoric acid. When this is done and the test tube is `washed it will be found that on its inside there will be produced an etched line at level 70, Figure l5. It is noted parenthetically that in Figures 13-16 the angle ,of tilt is exaggerated as compared to Figure 3, so that the devices and methods can be better illustrated. rihis line 7@ deines a plane of reference through the glass tube 58 which may be at any angle with reference to the axis of the tube 58 and rotated at any angle. piece of paper 71 having a straight edge around the glass tube 53 the low point ,of the etched line 70 can be read with a comparatively high degree of accuracy, this operation being illustrated in Figures l5 and 16. The low point is marked by a scratch line 73B. It has been noted l .turned in a direction such as would tighten the threads that the clinorneter body 52 is provided with an index mark at 72 reaching up over the coupling end as at 72A, and the glass tube S3 is likewise provided with an index mark on the side at 73 and also up over the top of the stopper, as at 73A. The lines 73--73A of the glass tube were aligned with the marks 7Z-72A of the clinometer body and hence were in a diametrical longitudinal plane normal to the surface 61 when the clinometer was in the hole. Hence, the marks 73-73A of the glass tube were likewise in a longitudinal diametric plane normal to the bit-detlector locating block 45, which plane also bisects the surface 28 and hence line 73-73A of tube 58 was in the direction the wedging surface 28 is directed,

regardless of how the surface 23 is located relative to the n.

The acid in the tube simultaneously writes its record of the angle (tilt) of the hole angle (or tilt) of the hole.

(namely line 7b). By then determining the lower point of the etched line 70 on the glass tube 5S, with reference to the scratch line 73 the operator can determine another line at 73B which is the lowest point on the etched line. lt is mere accident that lines 73 and 73B are at the same place on the tube shown in Figure 16, the more nsual case being that the two lines 73. and 73B are sepa- By wrapping a rated by a certain number of degrees. The angle between A.

`these lines 73 and 73B measured along a circular crosssection of tube 58 taken perpendicular to the axis of tube 58 is then read in degrees with a protraetor held normal to tube 58, and from this angle between lines 73 and 73B the driller determines the amount of rotation that must be provided for the bit-detiector 20 in order to correct the direction of the hole. The easy way to read the angle is to use a protractor with a hole in the center the size of the tube S3. The tube is then slipped through the hole in the protractor, which is thus in a plane normal to the axis of tube 58 and the angle between lines 73 and 73B d left, whichthus would cause-,the hole to bedellected even more to the left thanit already is and hence wouldbe in .the wrong,direction, whereas in Figure 5 the direction islas desired, namely touthe right, which then brings the axis oftheborevhole directly vertically. It will be appreciated,`howev er, Ythat any smaller angle than 180 degrees of rotation might be required as determined by the scratch lines 73 and the etching line 70.

'-Thej amount of ,rotation needed to re-position the bit-deector 20 is read from the marks 73 and '73Bv for any case as follows: y If the driller desires to dellectthe hole in a direction so as to bring it back towards vertical the angle between linesi.73jand` 73B subtracted from 180 degrees (i. e. the complement of `the angle between 73 and 73B) is determined and this complement angle is the amount of rotation to be applied to thebit-deflector 20. In the particular case illustrated herein the Figure 3 and Figure 5 positions were chosen ybcause they are easy to draw, and it is assumed that the Figure 3 position (off to the left) shows the hole headed in the wrong direction and that Figure 5k (vertical) is what is desired. With such assumptions, kand as shown in Figures 4 and 13-17, the clinometer reading showed zero degrees (0) between lines 73 and73B, and the complement of this reading is 180 degrees minus zero degrees or 1S() degrees. Accordingly, in this illustration it is necessary to re-position the bit-deflector 180 degrees from the origil nal (Figure 3) position by rotating it 180 degrees. Rotation can obviously be accomplished by turning the bit-deector and casing string 13 1 8() degrees either way, .and the direction of rotation chosen depends upon whether threads 22 of the bit-deflector and casing -13 are right or left hand. The casing 13 is always so as .to avoid loosening anyy coupling and thereby obtaining a false setting of the bit-del'lector.

- lf, however, the driller desires to deect the hole further from the vertical, the rotation or change of angle that is applied to casing 13'to re-position the bit-de'- fleetor is rnade equal to the angle between the index line 73 and the low point of the etch line, viz. 'mark 73B. Thusin the illustration herein, if the driller desires to increase the deflection to the left in Figure 3, he would read the angle 0 degrees between lines 73 and 73B and he would then notchangethe position of the bit-deflect'or 20, si'nce from the() degrees reading of theclinometer tube the driller would know that he `had' (by mere chance) happened to lower the bit-.detlector in the precise position (FigureS) in which, left wherek it is, it would produce the maximumy deflection of the hole in the direction the deflection is already headed.

Re-positioning of the bit-deector 20 by means of .casing string 13is accomplished by the driller as follows:

Achiselor other' markf47 is made on casing 13 aligned with one`of the index marks 48'(as in Figure 17), to show theftrst position of the casing 13 in the rst (random and incorrect) position, -shown in section in Figure 3. In the example illustrated herein casing 13 must be re-I positioned 180 degrees to bring it to the niark' at 42 inA Figure l7,.in .order t'o relocate member 20 to the Figure 5 position. The amount of rotation necessary for suchre-'posi'tioning having been determined, the nextoperation is that of turning the casing 13 and bit- .delectoi-ZI) the requisite number-of degrees (.180 degrecs in the illustrated instance) for correcting the direction of the hole. This 'is easily accomplished in, accordance with the present'inventio'n by lifting the` string of casing 13 ,with the bit-deector 20 attached thereto, and while they are in motion, that is to say, while casing `13 is being lifted, it isnr'otatedl the requisite number of degrees and the string of casing 13 then lowered to the new position.H This lifting, turningand `lowering asvaccomplilshed in one smoothvmotion.v Experienced opon loosening the couplings and hence throwing there` sults off. When the coupling threads 22 are left-hand threads, rotation is, of course, then in the left direction, as shown by dotted arrow L in Figure 13. i

After the bit-deflector 20 has been 4rotated bymeans of casing 13 and re-located in the correct position shown in Figure 5, a smaller bit, corresponding in diameter to the diameter of surface 28 of the bit-deector, is attached to the string 56 of drill rods, as shown in Figure 6, and is lowered through the casing y13. The

ing 13 is then rotated the requisite amount and the smaller hole 76 drilled. It will be, assumed that the deflection 'produced bythe bit-deiectorl 20 l(which corresponds to f ythe angle betweeny lines 31 yand 32 of Figures 3-5) `s not enough yto correct the tiltof'thehole,l although "it is a step in the rightl direction'. If this be true,*then as casing 13 i's pulled,'pr`eparatory-to reaming the hole 76 ja't'ithev rstsetting,` each coupling of the string 13 is marked with'v an index mark extending across the couplings, so asto allow,l them laterito '-be assembled ih'thef'sameconditionl"'Index mark 47, itw'ill be 'asbit 75 and rods 56 easily pass through the coupling at i 22 and slide along (but do not rotate against.) the surface 28 until the bit reaches the bottom end 26 where it displaced by the dimension 46 from Athe center line of the original hole.

Boring is then resumed, and thev `sumed,ha`s alreadyv vbeen rotated around to the correct position49 (whichcan be'any angle on quadrant48). Casing 13 is pulled straight up without rotation andas 'each' coupling cornes tothe level of quadrant 4,8, both yend s offthe casing at the coupling are kthenv marked, Vif

this has not been done during some previous operation.

Casing 13 carries the bitrdeector 20 landthe v,casing 13 and bit-deflector thus come out ofthe hole in acertain order and cant bere-assembled and lowered 'by converse'procedure and'with the coupling index marks'all aligned so that the bit-deector 20`r can later on be put smaller hole, as produced by the bit 75, is then drilled i l' down several feet, as at 76. Usually, itis desirable to drill 8 or l0 feet, or even farther, in the new direction 76. The direction is, of course, determined by the string 56 of drill tubes which are held in the corrected direcdownthe hole 'and re-located in exactly the same direction as it ywas previouslyQbut at fa somewhat deeper level after hole'76 produced by means' of the first setting is reamed out. Hence, the procedure of resetting the ybit-deflector 20, drilling the deflected hole 76 and reamtion by the wedging surface 28 of the bit-deector 20. it"

lt will be noted that rotation of bit 75 does not start until it has reached the lower end of member 20 and hence does not grind away the guiding surface 28. After hole 76 has been drilled, the rods 56 and bit 75 are.4 pulled, and then casing 13 and the bit-deflector v20 are pulled. Then to the larger size drill rods 11 (used, in Figures l and 2) there is attached a reaming bit at 78, Figure 7, having a tubular cylindrical pilot `at 79 provided with a tapered surface at the end 80. As the n bit 78 reaches the taper 17 originally produced, as in Figure 2, the tapered end 80 engages such surface and gradually guides the bit surface 78 toward the axis of hole 76. Drilling begins at 81, Figure 7, and gradually progresses along the line at 82, as shown in Figure 8. As the pilot 79 enters its full diameter into the hole 76, and as drilling progresses, the bit 78 begins rst to cut into the surface 17 and then to ream the hole 76 in the corrected direction producing the corrected hole of larger diameter 84, as shown in Figure 9. The corrected hole of larger diameter 84 is reamed down until the pilot 79 hits on the bottom 90 of the smaller hole 76. Then the string of rods 11, with the reaming bit 78 attached thereto are withdrawn from the hole, and the reaming bit is replaced by the standard bit 15 and reaming shell 12 of Figure 1. These can easily be lowered into the hole and past the point generally designated 100 at which direction is corrected. The surn face 17, where used, easily guides the large bit and reaming shell into the corrected direction portion 84 of the hole. As pointed out above, the taper bit 16 is preferably used. Where not used a shoulder remains at 101 and a longer taper at 80A (Figure 7) serves to guide the reamer 78 into the smaller hole 76, where a shoulder remains at 101, care must be exercised when the large bit is ever lowered past the shoulder.

Where the clinometer reading (etch line 70) shows an angular deviation which is more than can be corrected with the use of one setting of the bit deliector 20, or where a considerable deflection is for other reasons needed, this can be accomplished with only one setting of the clinometer as follows:

When the clinometer is set as in Figure 4 and withdrawn and read, the amount of rotation of casing 13 required to correct direction of the hole is known. Cas- 'ingcarifbe repeatedtime aftertime, always a little deeper down until the total deflection occasioned by the numerous individual settings Aaddsfup to the total angleo'fde- 'lection required'. This is accomplished without expendin'gmaterials beyond that occasioned' by normal wear.

Throughout the present ,specification and claims the `terminology used is that commonly employed in the diamond drilling business, but it will be understood that, while the Iinvention is most useful in diamond drilling, it islby no means limited thereto. Thus among'diamond drillers'the term, drill rod is used to designate the tubular pipeV which carries the p v i o'il-well drillers the termis drill pipe. Similarly diamond `drillers use the term deectingwedg'e, f as a name for the device used in changing the direction of a hole, whereas oil-well drillers call it a whip stock. The term sub-surface formations is used herein to mean formations below the overburden, whether designated rock or by some other term. Thus in the oil-well trade shale or soft sandstone is not called rock whereas mining engineers would so call it. The invention is accordingly, not to be considered as limited to any particular type of rotary drilling operation but is inclusive of all rotary drilling operations regardless of the particular jargon used. The device 50 has herein been designated as a clinometer, whereas in some quarters it is called an inclinometen The foregoing variations in nomenclature must not be regarded as limiting the scope or usefulness of the invention illustrated and claimed.

Throughout the foregoing explanation of the invenytion and in the claims it has been assumed that the borehole deection has been started by placing the deector 20 at the bottom of the hole but it will be understood that the driller can always back up and cement a plug in a hole at any desired level, and using the plug as a bottom, set the bit-deflector 20 thereon and carry through the operation of the invention as described. Hence the bottom 10A of the hole (Figures l and 2) should therefore be considered as either a natural formation or a plug cemented-in at a desired level in a much deeper hole. The manner of cementing-in a plug in a borehole is well known in the drilling art and need not be described in detail.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments herein.

bit, while amongl What I claim is: g l. The method of deecting substantially square bot,- tom bore holes of predetermined diameter which comprises determining the amount and angular direction of deflection of said bore hole from a predetermined bore hole direction, drilling the bottom of said hole to a taper, lowering into the bottom of the original hole a guide for defiecting a bit of smaller diameter from the direction of the hole at the point of placement of said guide and orienting said guide angularly for directing said smaller diameter bit in the desired bore hole direction, boring with a smaller diameter bit through the guide thus placed and.-

through the taper and thence onward so as to produce a smaller diameter extension of said bore hole in said desired direction below said taper, removing said smaller diameter bit and guide and reaming out said smaller diameter hole to said predetermined bore hole size.

2. The process of deecting a bore hole of predetermined diameter when said bore hole is drilled to a given depth in sub-surface formation which comprises lowering in-to said bore hole a guide having a shearableorienting surface thereon and a cylindrical longitudinal surface of smaller diameter than the bore hole, locating the position of the guide by reference to said orienting surface until said guide is oriented along an axis slightly out of line with the axis of said bore hole of predetermined diameter at the bottom of said bore hole, lowering a bit of said smaller diameter into the hole until it hits and shears off said orienting surface, then rotating said smaller diameter said smaller diameter bit and said guide and reaming said 5,.--1

smaller diameter extension to said predetermined diameter.

3. The process of claim 2 further characterized in that said extension is reamed by piloting a reamer of said predetermined diameter on the walls of said smaller diameter extension.

4. A drill guide for deecting bore holes in sub-surface formations comprising an elongated semi-circular bitdeecting member having inner and outer arcuate surfaces and having a short cylindrical portion provided with coupling threads on one end thereof, said cylindrical portion having a bore centrally thereof adapted to receive therethrough a drill rod and bit smaller than said bore, the outside diameter of said cylindrical portion being the same as the diameter of the outer arcuate surface of said semi-circular bit-deflecting member, the diameter of the bore of said cylindrical portion being the same as the diameter of the inner arcuate surface of said semi-circular bit-dellecting member, the longitudinal axis of the inner arcuate surface of said semicircular bit-deflecting member being inclined with respect to and spaced inwardly of the longitudinal axis of said outer arcuate surface of said semi-circular bit-deecting member, an inclinometer supporting land secured to said cylindrical portion within the bore thereof, said land having alaterally extending surface and a substantially vertical surface thereon and spaced from -the wall of said bore for supporting an inclinometer in a tixed longitudinal and transverse position with respectto said semi-circular bit-deilecting member, said inclinometer supporting land being secured to said short cylindrical portion by shearable means whereby said land may be detached in response to pressure exerted thereon by a drill rod and bit forced through said cylindrical portion after said inclinometer has been removed.

References Cited in the tile of this patent v UNlTED STATES PATENTS 1,806,509 

